RU2559482C2 - Titanium diboride producing method - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to powder metallurgy, namely, to the synthesis of titanium diboride, and can be used for the manufacture of ceramic armour, manufacture of heaters of high-temperature electric resistance furnaces, bathtubs and crucibles - metal evaporators, details of metal wires and electromagnetic pumps for pumping of the melted metals, chemical equipment units. The method of producing of titanium diboride consists in heating of the furnace charge from a mix of titanium dioxide, boron containing chemical reagent and carbon material at the temperature of 1500-1700°C within 20-25 minutes. Components of the furnace charge are mixed during common sifting. The carbon material is the high-disperse powder of nano-fibrous carbon with a specific surface density of 138-160 m²/g.

EFFECT: invention allows simplifying the process of titanium diboride producing.

Description

The present invention relates to powder metallurgy, in particular to the synthesis of titanium diboride, and can be used for the production of ceramic armor, the manufacture of heaters of high-temperature resistance furnaces, bathtubs and crucibles - metal evaporators, metal wire parts and electromagnetic pumps for pumping molten metals, components of chemical equipment.

A known method of producing titanium diboride by reducing powdered titanium dioxide with propane in the presence of boron powder in a nitrogen plasma stream (Galevsky G.V., Rudneva V.V. Features of boride formation in a plasma stream / Bulletin of the Mining and Metallurgical Section of the Russian Academy of Natural Sciences. Metallurgy Department: collection of scientific Proceedings / SibGIU - Novokuznetsk, 2010. - Issue 26. - S.111-116).

However, this method has the following disadvantages. The use of a combustible gas (propane) as a carbon source during depressurization of a plasma chemical reactor can lead to the formation of an explosive propane-air mixture. In addition, it is impossible to obtain pure, without impurities, titanium diboride by this process, since according to the X-ray diffraction analysis, the reaction products after quenching also contain titanium.

In addition, there is a method of producing titanium diboride (application US 2013/0251595 class. СВВ 35/04, 09/26/2013), which is a prototype of the invention and consists in heating a mixture from a mixture of titanium dioxide, a chemical reagent containing boron, and a carbon material [ 0042] at a temperature of 1500-1700 ° C for 20-25 minutes [0038] - [0041].

However, this method has a drawback. This is a mixture of the components of the charge in liquids, followed by drying of the suspension [0046], which complicates the process. As liquids, organic and inorganic materials with an acidic, basic or neutral reaction [0048] can be used. This disadvantage is associated with the relatively low dispersion of the used carbon materials, which are claimed to be: carbon black (soot), synthetic carbon (artificial graphite) and calcined petroleum coke (calcined petroleum coke) [0042] - [0045]. Information about their dispersion (or specific surface area) is not given in the prototype text. However, it is known [Gruner W., Stolle S., Wetzig K. Formation of CO _x species during the carbothermal reduction of oxides of Zr, Si, Ti, Cr, W and Mo. International Journal of Refractory Metals & Hard Materials 18 (2000) 137-139], that the specific surface area of carbon black is 80.2 m ² / g and that of graphite powder is 19.5 m ² / g. It is also known that calcined petroleum coke [Sosedov V.P., Chalykh E.F. Graphitization of carbon materials. - M.: Metallurgy, 1987, p. 23.] is a raw material for producing graphite. Therefore, we can assume that under the same grinding conditions of calcined petroleum coke and artificial graphite, the dispersion values (and specific surface area) of the powders of these materials will be comparable.

The task of the invention is to simplify the process.

This object is achieved in that in the known method for producing titanium diboride, which consists in heating the mixture from a mixture of titanium dioxide, a chemical reagent containing boron, and a carbon material at a temperature of 1500-1700 ° C for 20-25 minutes, the mixing of the components of the mixture is carried out at joint sifting, and as a carbon material, a finely dispersed nanofiber carbon powder with a specific surface of 138 ... 160 m ² / g is used. A nanofibrous carbon powder is obtained by grinding in a mortar of its granules 4-8 mm in size, prepared by catalytic decomposition of gaseous saturated hydrocarbons on a nickel catalyst at a temperature of 550 ° C. The granules are formed by tightly interwoven nanofibrous carbon fibers up to 4 microns in length and 10-100 nm in diameter (average diameter 73 nm). The content of impurities (catalyst residues) in the nanofiber carbon is small and does not exceed 1% of the mass. The use of nanofiber carbon as the carbon material leads to the following. Since the specific surface area of nanofibrous carbon is much higher than that of soot, artificial graphite, and calcined petroleum coke, when mixing reagents (titanium dioxide, a chemical reagent containing boron, and

carbon material - in this case, carbon nanofiber) provides a closer contact between the solid particles of the reagents. This, in turn, helps to increase the intensity of the synthesis of titanium diboride. For this reason, there is no need for additional operations (mixing the components of the mixture in liquids with subsequent drying of the suspension), complicating the process.

The method is as follows. Powders of titanium dioxide, boron carbide and carbon material (nanofiber carbon) with a specific surface area of 138 ... 160 m ² / g are sieved through a sieve with a mesh size of 100 μm. When sifting, the components of the mixture are mixed. Next, the charge is loaded into a crucible of glassy carbon with an inner diameter of 15 mm and a height of internal space of 60 mm. Then the internal volume of the crucible is 10.603 cm ³ . At a charge density of 2.5 g / cm ^3, its mass is approximately 26 g. A glass-carbon crucible is closed with a graphite lid and placed in a quartz reactor, which, in turn, is inserted into the inductor of the induction furnace. To prevent boron carbide nitriding, the quartz reactor is purged with argon. The mixture is heated at a temperature of 1500 ... 1700 ° C for 20 ... 25 minutes.

The temperature in the reactor is controlled by an optical pyrometer. After cooling of the reactor, the argon supply is stopped, the crucible is removed from the reactor, and the reaction product (titanium diboride powder) is precipitated from the crucible.

At temperatures below 1500 ° C, titanium diboride does not form, as evidenced by the absence of its reflections in the diffraction patterns. At temperatures exceeding 1700 ° C, unproductive energy costs occur. When the process time is less than 20 minutes, titanium diboride is not formed, as evidenced by the absence of its reflections in the diffraction patterns. When the process time is more than 25 minutes, unproductive energy consumption takes place. When the specific surface area of the nanofibrous carbon powder decreases below 138 m ² / g for 25 minutes and a temperature of 1700 ° C, it turns out to be insufficient for the complete formation of titanium diboride, as evidenced by the presence of titanium dioxide and boron carbide on the diffraction patterns of reflections. An increase in the specific surface area of nanofibrous carbon powder above 160 m ² / g is impossible at any grinding time.

Thus, the proposed method allows to simplify the process.

An example implementation of the invention

Powders of titanium dioxide, boron carbide with an average particle size of 0.8 μm and nanofiber carbon with a specific surface of 144 m ² / g are sifted together through a sieve with a mesh size of 100 μm. Next, the finished mixture is poured into a crucible of glassy carbon. The crucible is closed with a graphite lid and placed in a quartz reactor, which in turn is inserted into the inductor of the induction furnace. A quartz reactor is purged with argon. The process temperature is 1600 ° C, the exposure time at this temperature is 22 minutes. X-ray phase analysis revealed the presence in the reaction products (heat-treated mixture) of only one phase - titanium diboride.

Claims (1)

The method of producing titanium diboride, which consists in heating the mixture from a mixture of titanium dioxide, a chemical reagent containing boron, and a carbon material at a temperature of 1500-1700 ° C for 20-25 minutes, characterized in that the mixture of the components of the mixture is carried out by joint sieving, and as a carbon material, a highly dispersed nanofiber carbon powder with a specific surface of 138-160 m ² / g is used.